arm64: dts: meson-gx: fix i2c compatible

This fixes the following DT schemas check errors:
meson-gxbb-nanopi-k2.dt.yaml: i2c@8500: compatible: Additional items are not allowed ('amlogic,meson-gxbb-i2c' was unexpected)
meson-gxbb-nanopi-k2.dt.yaml: i2c@8500: compatible:0: 'amlogic,meson-gx-i2c' is not one of ['amlogic,meson6-i2c', 'amlogic,meson-gxbb-i2c', 'amlogic,meson-axg-i2c']
meson-gxbb-nanopi-k2.dt.yaml: i2c@8500: compatible: ['amlogic,meson-gx-i2c', 'amlogic,meson-gxbb-i2c'] is too long

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>